Monarch of Evernight - Volume 1 - Chapter 1: Crimson Colored Night

The number one swordsman Zhao Jiangui is the martial world’s best hope for peace: All he has to do is seduce the Demon Sect Leader.

Overnight, Tangning became a big slave owner in the southern United States with three large plantations and hundreds of black slaves who could be driven at will.

Tangning was very satisfied with the result of such a time-travel, but then he sadly discovered that he could only enjoy three years of such a good life, because three years later would be the “Civil War”, what should he do after this?

- Description from novelbuddy

He was once Head of the Immortal Sects.

Jiang Zheliu resisted the world’s destruction, protecting the people single-handedly. After losing all his spiritual energy, his hair turned white overnight.

All that remained was a millennium passed in vain, and a grave disease.

He distanced himself from the Cultivation World, went to Zhongnan Mountain to collect herbal medicines and grow flowers, as if to retire.

Until….. Those little demons he had once saved, his cherished juniors, even those devils that he had suppressed innumerable times, all came knocking at his door, each more excited than the next gripping his hand:

“Qianbei, what type do you like? Can you not be so rigid on your requirements?”

Jiang Zheliu: “……？？？”

Wenren Ye is newly appointed Devil Lord of the Devil Realm.

He is cold-hearted, devilishly handsome, and when he was younger he suffered a humiliating defeat at the hands of a certain Head of the Immortal Sects.

Still obsessed with this defeat, Wenren Ye hurried through the night to Zhongnan Mountain, but all he saw was white-haired weak Immortal Sects Leader, with droopy eyes, sick to the bone, with freshly coughed up blood staining his lips.

His obsession was still alive, but his heart was also thumping.

- Description from Novelupdates

The story is about a a hitman, Who dies because of his own recklessness and transmigrates into a game he used to play after his retirement as a hitman.I'm not gonna spoil any further, but i might answer few of your questions.Is MC overpowered?Nope, he'll become strong over time and all battle he'll fight will be because of his effort and techniques.Is there magic and adventure?Yes! It have both magic like normal isekai with adventure and fighting with monsters and many other things. There are other important things like “Essence Stone” But let's talk about it in the chapters.There will be harem?Not really, He will be in contact with many beautiful female and males but one waifu but i haven't decided yet.All i can say is, give it a try, I'll try my best to make it worth your time.